Enclosed fuse



N. RAPP ENCLOSED FUSE Jan. 10, 1939.

Original Filed March 4, 1936 Ihvehto'r Nicolaus RQD'P,

9 is Attorneg.

Patented Jan. 10, 1939 UNITED STATES ENCLOSED FUSE Nicolaus Rapp, Annaberg, Erzgebirge, Germany,

assignor to General Electric Company, a corporation of New York Application March 4, 1936, Serial No. 67,140. Re-

newed March 30, 1938. In Germany March 7,

13 Claims.

The present invention relates to fuses and has for a principal object the provision of improvements in a fuse of the enclosed type wherein an are formed upon operation of the fuse is extinguished by means of gases or other medium developed due to the heat of the arc.

In the manufacture of enclosed fuses, it has been the practice commonly employed to construct the enclosing casings or envelopes for the fuses of compressed insulating material, such for example as fibre, kraft paper and the like, rather than of ceramic material, in order that the casings or envelopes may be less susceptible to breakage due to shocks and bending. Such construction has the advantages, among others, that it renders the employment of reenforcing bands unnecessary and also facilitates the mounting of the fusible conductors within the casings or envelopes. It has been known, also, to construct fuses having within their enclosing casing a material capable of developing an arc quenching medium upon being subjected to the heat of an are formed upon operation of the fuse. Some fuses of this type have been constructed with the material for developing the arc quenching medium uniformly distributed throughout a filler of sand or other suitable inert material. It has been found, however, that fuses of this type have the disadvantages, among others, over fuses provided only with a sand filler, that upon heavy short circuit currents back-ignitions are likely to take place or the fuse casings are likely to burst as a result of fuse operation.

In the practice of the present invention also it is contemplated to employ in an enclosed fuse a material or composition capable of developing arc quenching medium upon being subjected'to the heat of an arc. However, the disadvantages experienced heretofore with this type of fuse are obviated by the arrangement, in accordance with the present invention, of the fusible conductors and the material or composition for developing the arc quenching medium within the enclosing casing of the fuse in such manner that only portions of the fusible conductors are in proximity or contact with the said material or composition while the remainder of the space within the fuse casing and surrounding the fusible conductors is filled only with an inert material such as sand.

For an understanding of further objects of the invention and of that which I believe to be novel and my invention, attention is directed to the following detailed description and the claims appended thereto, taken in conjunction with the accompanying drawing in which are illustrated diagrammatically several exemplary forms of enclosed fuse embodying the present invention.

In the drawing, Fig. 1 is a partial longitudinal section through an enclosed fuse illustrating one method of carrying out the invention and Fig. 2 illustrates a modification of the fuse construction of Fig. 1; Fig. 3 is a partial longitudinal section through an enclosed fuse illustrating a second method of carrying out the invention, and Figs. 4, 5 and 6 illustrate modifications of the fuse construction of Fig. 3; Fig. 7 is a transverse section through a fuse constructed for practicing the invention in a manner similar to that employed in the constructions of Figs. 1 and 2; Fig. 8 is a transverse section through a fuse similar to those of Figs. 1 and 2; Fig. 9 is a transverse section through a fuse similar to those of Figs. 4 and 5; Fig. 10 is a transverse section through a fuse similar in construction to that of Fig. 9; Fig. 11 is a transverse section through a fuse similar to that of Fig. 6; Fig. 12 illustrates a modification of the fuse construction of Fig. 8; Fig 13 illustrates a modification of the fuse of Fig. 7; Fig. 14 illustrates a modification of the fuse of Fig. 11; Fig. 15 is a transverse section of a fuse illustrating a method for carrying out the invention similar to that employed in the fuse construction of Fig. 3; and Fig. 16 illustrates a modification of the fuse construction of Fig. 3.

In Fig. 1 of the drawing, a designates an enclosing casing which is cylindrical or tubular and which is constructed of a compressed insulating material capable of developing arc quenching gases or other medium when subjected to the heat OI an arc. Numerous expedients for accomplishing this desired purpose are well known and commonly employed in the art. For example, the

casing or tube may be made solely of a compressed I material, such as horn fibre or kraft paper, capable of developing arc quenching gases, or may be made of compressed fibre or paper impregnated or bound together with any well known composition, such as an alkyd resin, which is capable of developing the arc quenching gases. Also, a tube or casing constructed of paper or fibre may be lined with a boric acid compound or other similar and well known compound capable of developing arc quenching gases, or such compound may be made in a form in which it is mechanically self-sustaining and therefore can be used by itself, without paper or fibre backing, for the tube or casing.

Within the tubular casing a are disposed one or more fusible conductors b, two being shown in the exemplary embodiment of Fig. 1, which are so shaped and arranged that they are in contact with the inner surface of the tubular casing a at the points 0, which in the embodiment of Fig. l are substantially midway of the enclosing tubular casing. In the modification of Fig. 2, the fusible conductors are brought into contact with the inner surface of the enclosing casing at several spaced apart points along the length of the casing. Also disposed in the enclosing casing and completely surrounding the fusible conductors except at their points of contact with the :asing, is

' a body s of relatively finely divided inert insulating filler material, such as sand, which is capable of effectively dissipating the heat and gases developed upon operation of the fuse. With this arrangement, when the fusible conductors 'melt and arcs are formedat the points 0, arc quenching gases are given off from the adjacent points on the inner surface of the enclosing casing and these gases quickly quench the arcs. It has been found that with a construction of the type described, especially when employed in heavy duty fuses, the duration of the arcing is extremely short which is of importance with respect to the selectivity of the fuses and also with respect to switching operations on electric systems in which the fuses may be connected. An important advantage of the fuse construction just described is that due to the limited area of the enclosing casing which is caused to develop gases, an insufficient volume of the gases is devloped to produce rupture of the casing, although the amount of the gases is sufiicient effectively to quench the arcs formed upon rupture of the fusible conductors.

In the fuse construction of Fig. 3, the fuse conductors b are arranged in such a manner that they extend substantially parallel with the axis of the enclosing casing a, and it is contemplated that the conductors be surrounded with the sand or other inert filler s in the same manner as in the construction of Fig. 1. Embedded in the filler and surrounding the conductors at one or more points along the lengths thereof are small bodies or inserts d of a material or composition capable of developing arc quenching medium upon being subjected to the heat of an arc. Numerous materials or compositions suitable for making the beads or inserts d are well known and commonly employed in the art and may be, for

1 example, barium chlorate and other chlorates or perchlorates, calcium and magnesium carbonate, boric acid or sulphur. These beads or inserts act in the same manner to produce arc quenchingmedium upon the formation of an are at the adjacent points of the fusible conductors as was described in connection with the small areas of the enclosing casing a at the points 0 in the construction of Fig. 1.

In the construction of Fig. 4, an insert of gas developing material in the form of a ring eis disposed in the inert filler s substantially midway of the length of the enclosing casing a and is arranged in surrounding contacting relation with respect to the conductors b. In the construction of Fig. 5, several of these rings a are disposed at spaced points along the lengths of the conductors b.

An insert, in the form of a disc 1, of suitable material capable of developing arc quenching medium upon being subjected to the heat of an arc, is provided in the construction of Fig. Sand is arranged between and in contact with the conductors b.

An arrangement for accomplishing the objec-= tives of the present invention in a manner similar to that employed in the constructions of Figs. 1 and 2 is shown in Fig. 7 wherein is illustrated an enclosing casing a having interior projections or ledges g in contact with which are three fusible conductors b. In this case either the whole casing or only the projections may be constructed of material capable of developing arc quenching medium in the manner previously set forth. It will be understood of course that the number of projections or ledges will be determined by the number of fusible conductors and by-the spacing of the projections or ledges along the lengths of the conductors.

The construction illustrated in transverse cross-section in Fig. 8 is similar to those of Figs. 1 and 2 except that three fusible conductors b are employed and arranged in contact at predetermined points 0 with the inner surface of casing w.

Likewise, the construction illustrated in Fig. 9 is similar to those of Figs. 4 and except that three fusible conductors b are employed with the ring or rings e disposed in surrounding relation to the conductors.

In the construction illustrated in Fig. 10, the ring or rings e are placed on the inside of the three fusible conductors b, instead of outside thereof, and are in contact with the conductors.

Fig. 11 illustrates a construction similar to that of Fig. 6 with the exception that the disk I has in contact therewith three fusible conductors instead of only two.

In the practice of the present invention it is not absolutely necessary that the fusible conductors be in direct contact either with the enclosing casing or with the inserts as the case may be. It is sufficient, in order to attain the objectives of the present invention, that the conductors be only in close proximity to the enclosing casing or to the inserts. Such an arrangement is illustrated in Fig. 12 which shows a construction similar to those of Figs.- 1 and 2 with the exception that three fusible conductors are employed and. are arranged only in close proximity instead of in direct contact at spaced points along their lengths with the inner surface of the enclosing casing. Similarly, the three conductors in the construction of Fig. 13 are not in direct contact with the projections or ledges g but are disposed merely in proximity thereto. Other- Wise the construction of Fig. 13 is the same as that of Fig. 7. In the same manner the construction of Fig. 14 differs from that of Fig. 11.

In'the construction of Fig. 15, three fusible conductors b are employed and are arranged so that they extend freely through the tubular enclosing casing a. In this case inserts or beads h, of a material capable of developing an arc quenching medium upon being subjected to the heat of an arc, are disposed in proximity to but not in direct contact'with the fusible conductors. Likewise, in the construction of Fig. 16, the fusible conductors b are surrounded by but not in direct contact with small inserts i of a material or composition capable of producing arc quenching medium upon being subjected to the heat of an arc.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. In a. fuse device, an enclosing casing, means within said casing comprised of material capable of developing an arc quenching gas upon the formation of an arc in proximity thereto, a fusible conductor arranged in said casing in such mannor that only a relatively small part of the conductor is in proximity to said means, and a body of sand substantially filling the remainder of the space within said casing.

2. In afuse device, an enclosing casing, a filler of sand disposed in said casing, a. fusible conductor having a portion extending through and embedded in said filler of sand, and a body of material disposed substantially in contact with the surface of another portion of said conductor which said material is capable of giving off an arc quenching medium upon the formation of an are due to fusion of said other portion of the fusible conductor.

3. In a fuse device, a body of relatively finely divided inert material, a. fuible conductor having a substantial portion thereof embedded in said body of inert material, and means in close proximity with another portion of said conductor for giving off an arc quenching medium upon being subjected to the heat of an arc.

4. In a fuse device, a body of relatively finely divided inert material, a fusible conductor embedded in said body of material, and means in close proximity with portions of said conductor spaced apart along the length of the conductor which said means includes a material for supplying arc quenching medium adjacent said spaced apart portions of the conductor upon formation of an are due to fusion of said spaced apart portions.

5. In a fuse device, a fusible conductor, means substantially in contact with portions of said conductor spaced apart along the length thereof including material capable of developing arc quenching medium upon being subjected to the heat of an arc, and bodies of relatively finely divided inert material disposed in contact with said conductor intermediate said means.

6. In a fuse device, an enclosing casing having at its inner surface material capable of producing an arc quenching medium upon being subjected to the heat of an arc, a fusible conductor arranged in said casing with a portion of the conductor in close proximity to the inner surface of the casing, and a body of relatively finely divided inert material disposed in said casing and substantially completely embedding the remainder of said conductor.

'1. In a fuse device, an enclosing casing having at its inner surface material capable of producing an arc quenching medium upon being subjected to the heat of an arc, a body of relatively finely divided inert material disposed in said casing, and a fusible conductor embedded in said body of inert 1 material and arranged in substantial contact with the inner surface of said casing at spaced intervals along the conductor.

8. In a fuse device an enclosing casing having spaced apart projections on the inner surface thereof which projections include a material for supplying arc quenching medium upon the occurrence of an arc in proximity thereto, a body of relatively finely divided inert material substantially filling the interior of said casing, and a fusible conductor extending through said body of inert material and arranged with portions of the conductor in relatively close proximity to said projections.

9. In a fuse device, a body of relatively finely divided inert material, a fusible conductor embedded in said body of inert material, and means embedded in said body of inert material and relatively concentrated in close proximity to a portion of said conductor including a material capable of developing an arc quenching medium upon being subjected to the heat of an arc formed upon fusion of said portion of the conductor.

10. In a fuse device, a body of relatively finely divided inert material, a fusible conductor embedded in said body of inert material, and a plurality of relatively small bodies embedded in said body of inert material and arranged substantially in contact with said conductor respectively at spaced points along the conductor, said bodies including material capable of giving off arc quenching medium when subjected to the heat of an arc.

11. In a fuse device, an enclosing casing, a fusible conductor extending through said casing, a plurality of bodies disposed in substantial contact with said conductor at spacedintervals along the length of the conductor and comprising material capable of developing arc quenching medium upon being subjected to the heat of an arc, and a filler of sand disposed in said casing and embedding said conductor intermediate said bodies of first mentioned material.

12. In a fuse device, an elongated fusible conductor, a body of relatively finely divided inert material arranged in contact with the surface of said conductor over a substantial portion of the conductor length, and means comprised of material capable of giving off arc quenching medium upon occurrence of an arc in proximity thereto,

arranged in contiguity with the conductor over another portion of the conductor length.

13. In a fuse device, an elongated fusible conductor, a body of sand arranged in contact with the surface of the conductor over a substantial portion of the conductor length, and means comprised of material capable of giving oil! are quenching medium upon occurrence of an arc in proximity thereto, arranged in contiguity with the conductor over another portion of the conductor length.

NICOLAUS RAPP. 

